The enlarged left hilar shadow should be considered for pulmonary inflammation, hilar lymph node enlargement, or even hilar tumor occupancy. If there is chronic heart disease, it is also important to look for vascular hilar enlargement caused by protrusion of the aortic arch. In this case, it is necessary to do chest enhancement CT, chest high-resolution CT, and fiberoptic bronchoscopy if necessary, to understand microscopically whether there are enlarged lymph nodes or foreign bodies in the lumen, including tumor sputum and inflammatory infections. If, after regular antibiotic anti-infection treatment, the left hilar shadow enlargement is significantly reduced, it is considered to be a common infectious disease. If the hilar shadow still does not change significantly or shows enlargement after corresponding treatment, further PET-CT is needed to clarify whether it is early malignant tumor, and if necessary, mediastinal thoracoscopy can be performed to clarify the pathological nature and thoroughly investigate whether there is a possibility of tumor.